This invention relates to plastic bags capable of withstanding external force applied to the bag, and more particularly to plastic bags which have an open end which may be folded over upon itself, and a pocket which may be turned inside out and over the folded open end providing a pressure resistant closure. Such bags are suitable for a wide variety of uses such as medical ice pouches.
A variety of plastic bags have been developed which hold gases, liquids or solids. Two sheets of plastic may be sealed together, or a single sheet may be folded over itself to form two sheets and sealed together to form an enclosure which withstands both the internal forces of the bag contents and external forces which may be applied to the bag. However, it is desired to provide bags having an open end so that the bag may be filled by the user and later emptied and re-used or the contents may be partially withdrawn and the bag reclosed. Various means have been used to close the open end when the bag is filled, depending upon the contents of the bag and requirements of the particular application. For example, bags similar to those shown in U.S. Pat. No. 2,709,467, Australian Pat. No. 263,997, and British Pat. Nos. 1,546,419 and 1,067,391 may be used to contain solid materials, but do not provide a liquid or gas tight closure. U.S. Pat. No. 2,709,467 describes a closure at the top of a bag body having a flap which folds over the top, not providing a gas or liquid tight closure, for use in shirt bags and the like. Australian Pat. No. 263,997 shows bag closure flaps similar to those in U.S. Pat. No. 2,709,467, which also do not provide a gas or liquid tight closure. British Pat. No. 1,546,419 discloses a coin bag having a flap which covers the mouth of the bag and a reversible pocket which may be folded over the mouth and flap. Coins are retained in the bag but gases and liquids would escape. British Pat. No. 1,067,391 teaches the use of a bag having a panel into which the open end portion of the bag may be inserted. Such bags are suitable for sweaters and the like because they keep their contents clean without gas or liquid tight closure of the bag, and the contents may be removed for examination and replaced in the bag. Such bags are not useful for holding gases or liquids.
A gas or liquid tight closure for plastic bags is disclosed in U.S. Pat. No. 3,299,927, which has a filling neck which may be folded over upon itself and a flexible strap extending beyond the edges of the neck at the top opening. The ends of the strap may be snapped around the folded neck to hold it in place. In another similar embodiment, the snap has been omitted and a stiff strap has been used in place of the flexible strap. The stiff strap may be bent around the folded neck with the fingers, and retains the folded neck portion to some extent. Such bags may be filled with ice or water and used by hospital patients to relieve pain or enhance healing. These bags are not sufficiently resistant to external forces when containing more than 1/3 of the bag volume of liquid and tests have shown the closure will unwind and all bags opened when between 50 and 65 pounds of external force was applied to bags having a 31/4 inch inside neck width.
Bags should withstand at least about 75 pounds of external force to be used safely by medical patients for ice or hot water bags and for other uses. Thus, there is a need for plastic bags which resist relatively substantial external forces without leaking.
Accordingly, an object of this invention is to provide a flexible plastic bag for holding gases, liquids, or solids.
Another object is to provide a flexible plastic bag which securely retains liquids or gases and is capable of withstanding, where needed for the particular applications, external forces of greater than 75 pounds.
Yet another object is to provide a flexible plastic bag having an open end which may be twisted or folded over upon itself, and a pocket which may be turned inside out over the twisted or folded open end to form a closure which is resistant to external forces.